In many countries the operators and Internet service providers are today obliged by legal requirements to provide stored traffic data generated from public telecommunication and Internet services for the purpose of detection, investigation and prosecution of crime and criminal offences including terrorism.
There are also a number of initiatives within the European Union (EU) to regulate the legal basis for data retention. The EU Parliament has recently adopted a set of amendments and by that approved the Council's proposed directive on data retention, see Directive 2006/24/EC of the European Parliament and of the Council of March 2006 on the retention of data. This proposal describes not only initial requirements, but also how an extension of the directive will be handled. Consequently, an essential part of the operator's effort to comply with current legislation will be to secure that processes and tools are adaptable to handle an expansion of the scope for data retention.
This clause presents the user requirements related to the retained data of telecommunications with the LEA being the user. The relevant terms are defined in clause 3.1. These user requirements are subject to national law and international treaties and should be interpreted in accordance with applicable national policies.
ETSI TS 102 657 V1.7.1 (2010-10) gives guidance for the delivery and associated issues of retained data of telecommunications and subscribers. It provides a set of requirements relating to handover interfaces for the retained traffic data and subscriber data by law enforcement and other authorized requesting authorities. The requirements are to support the implementation of Directive 2006/24/EC of the European Parliament and of the Council of 15 Mar. 2006 on the retention of data.
ETSI DTS/LI-00033 V0.8.1 contains handover requirements and a handover specification for the data that is identified in EU Directive 2006/24/EC on retained data.
The ERICSSON® AUTOMATIC DATA RETENTION SYSTEM DRS™ provides a solution for collecting, storing and delivering communication data generated by telecommunication and Internet services in public fixed and mobile networks. FIG. 1 belongs to the prior art and discloses the Handover Interfaces HIA 7 and HIB 8 between a Data Retention System DRS 2 at a Communication Service Provider CSP 1, and an Authorized Organization AO 3. The figure shows an Administration Function AdmF 4 used to handle and forward requests from/to the AO. A Mediation and Delivery function MF/DF 5 is used to mediate and deliver requested information. Storage 6 is used to collect and retain data from various Network elements. The interfaces through which the CSP receives requests from the Authorized Organization, and transmits responses and information are denoted as Handover Interfaces. The generic Handover Interfaces adopt a two port structure such that administrative request/response information and Retained Data Information are logically separated. The Handover Interface HIA 7 transports various kinds of administrative, request and response information from/to the Authorized Organization and the organization at the CSP which is responsible for Retained Data matters. The Handover Interface HIB 8 transports the retained data information from the CSP, to the Authorized Organization AO. The HIA and HIB interfaces may be crossing borders between countries. This possibility is subject to corresponding national law and/or international agreements.
Hierarchical Storage Management (HSM) is a data storage technique which automatically moves data between high-cost and low-cost storage media. HSM systems exist because high-speed storage devices, such as hard disk drive arrays, are more expensive (per byte stored) than slower devices, such as optical discs and magnetic tape drives. While it would be ideal to have all data available on high-speed devices all the time, this is prohibitively expensive for many organizations. Instead, HSM systems store the bulk of the enterprise's data on slower devices, and then copy data to faster disk drives when needed. In effect, HSM turns the faster disk drives into caches for the slower mass storage devices. The HSM system monitors the way data is used and makes best guesses as to which data can safely be moved to slower devices and which data should stay on the fast devices.
In a typical HSM scenario, data files which are frequently used are stored on disk drives, but are eventually migrated to tape if they are not used for a certain period of time, typically a few months. If a user does reuse a file which is on tape, it is automatically moved back to disk storage. The advantage is that the total amount of stored data can be much larger than the capacity of the disk storage available, but since only rarely-used files are on tape, most users will usually not notice any slowdown.
HSM is sometimes referred to as tiered storage and it is often used for deep archival storage of data to be held long term at low cost. Automated tape robots can silo large quantities of data efficiently with low power consumption.
In the Data Retention case, when the Authorized Organization AO 3 sends query requests towards the retention system 2, there could be cases where the response time could be differentiated for different subset of data to be returned:                When different sets of data are stored in different performing storage devices 6; the resulting data could be sent to the AO with different response times;        When different sets of data are stored in different retention systems (possible way to scale the ADRS solution); the resulting data from different retention system could have different response times.        
A problem occurs when the agency sends a request to DRS which could send different result sets with different delays; in such case the agency is not aware in advance of this differentiated response times and will not be able to process the retrieved data in a controlled way.